The 'Roar' hitmaker split with the 'Gravity' singer earlier this year after 18 months of dating and though she insists there is no bitterness between them, she has pledged to make her feelings public through song.

Speaking to Cosmopolitan magazine - for which she appears on the cover of 62 international editions - she said: ''There's no bad blood. But I'm sure there will be inspired songs.''

However, 36-year-old John isn't worried about the lyrical content of Katy's songs.

The 'Half Of My Heart' singer went on to insist he would be happy to see his former flame's tracks go to number one in the chart - and claimed he has deliberately sabotaged his own career to give other artists a chance.

Asked if he wants Katy's songs about him to go to number one, he said: ''I actually want everybody's song to go number one. I purposely stopped writing hits to give other people a chance to have number one songs. I just stand to the side.''